Sealed class

A class which cannot inherits is called as sealed class

Sealed class classname

{

}

Note: all static classes are equal to static classes.

Sealed class A

{

Public int x=100;

}

Class Demo

{

Public static void Main()

{

A obj=new A();

Console.writeline(obj);

}

}

            

Sealed classes:

1)Can create instances, but cannot inherit

2)Can contain static as well as nonstatic members.

Static classes:

1)Can neither create their instances, nor inherit them

2)Can have static members only.

sealed class and sealed method

1.  A class, which restricts inheritance for security reason is declared, sealed class.
2.  Sealed class is the last class in the hierarchy.
3.  Sealed class can be a derived class but can't be a base class.
4.  A sealed class cannot also be an abstract class. Because abstract class has to provide functionality and here we are restricting it to inherit.
Practical demonstration of sealed class

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

 

namespace sealed_class

{

    class Program

    {

        public sealed class BaseClass

        {

           public void Display()

        {

                        Console.WriteLine("This is a sealed class which can’t  be further inherited");

              }

  }

 

        public class Derived : BaseClass

        {

           // this Derived class can’t inherit BaseClass because it is sealed

        }

   

        static void Main(string[] args)

        {

            BaseClass obj = newBaseClass();

 

            obj.Display();

 

            Console.ReadLine();

        }

    }

}

sealed method

  Sealed method is used to define the overriding level of a virtual method.

  Sealed keyword is always used with override keyword.

  Practical demonstration of sealed method

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

 

namespace sealed_method

{

    class Program

    {

        public class BaseClass

        {

           

            public virtual void Display()

            {

                Console.WriteLine("Virtual method");

            }

        }

 

       publicclass DerivedClass: BaseClass

        {

          // Now the display method have been sealed and can’t  be overridden

            public overridesealed voidDisplay()

            {

                Console.WriteLine("Sealed method");

            }

        }

 

       //public class ThirdClass : DerivedClass

       //{

 

       //    public override void Display()

       //    {

       //        Console.WriteLine("Here we try again to override display method which is not possible and will give error");

       //    }

       //}

 

        static void Main(string[] args)

        {

 

            DerivedClass ob1 = newDerivedClass();

            ob1.Display();

 

            Console.ReadLine();

        }

    }

}